Mobile Adhoc Network (MANET) consists of a collection of wireless mobile hosts without the required intervention of any existing infrastructure or centralized access point such as base station. The dynamic topology of MANET allows nodes to join and leave the network at any point of time. Wireless MANET is particularly vulnerable due to its fundamental characteristics such as open medium, dynamic topology, distributed cooperation and constrained capability. So security in MANET is a complex issue. There are many routing protocols that establish the routes between the nodes in the network. The control towards the management of the nodes in the MANET is distributed. This feature does not give assurance towards the security aspects of the network. There are many routing attacks caused due to lack of security. In this paper, therefore, we attempt to focus on analyzing and improving the security of one of the popular routing protocol for MANET viz. the Adhoc On Demand Distance Vector (AODV) routing protocol. Our focus specifically, is on ensuring the security against the Black hole Attack. A black hole is a malicious node that falsely replies for any Route Requests (RREQ) without having active route to specified destination and drops all the receiving packets. If these malicious nodes work together as a group then the damage will be very serious. The proposed solution is capable of eliminating the effect of presence of black hole nodes in the MANET. The simulation study is performed using Network Simulator NS-2.34.